Page 124 - Math Genius C3

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ray 4. Look at the picture and answer the
Get it right! following questions.
A ray is a part of a line that starts at one point and can P Q (a) The sunlight is an example of which one:
be extended in one direction endlessly. The figure shows a ray, a ray, a line or a line segment?

QP . PQ (b) Count the number of line segments in the

(because its initial point is P.) boat.
As we can see in the given figure that a ray AB begins
from point A and goes towards B. B is just a point on the ray, not its end. This ray is denoted (c) At how many points do vertical and horizontal line segments meet?

by AB , where A is its initial point. Logical Thinking Be Aware
Think Tank • We need at least two points to
Light coming from a torch and a bulb are examples of rays. draw a line segment.
Horizon is the place where the earth and sky appear • A point and a line have no
to meet. Is the horizon an example of a line? thickness.
practice time 7a

1. Name the following figures in two ways. One has been done for you. measurinG and drawinG a line seGment

Y A N measuring a line segment
A line segment has a definite length, so it can be measured and drawn
M
(a) X (b) B (c) (d) P Q on paper.

Line segment XY A ruler is used to measure the length of different line segments. Each ‘cm’ is divided into

XY 10 equal parts, called mm (millimetre).
To measure the length of a line segment, we follow the steps as given below:
2. How many line segments are used to form each of the following shapes? Name

them. 1. Place a ruler along the line segment, say PQ.

A D P G E J 2. Align the starting point of the line segment with the zero mark of the ruler. Remember
to adjust ‘0’ on the ruler at point P. P Q
(a) (b) (c) H K (d) F I
3. Read the mark on the ruler against the 0 cm 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
other point Q on the ruler. It ends at 0 1 2 3 4 5 6
B C Q R I J G H
3. How many lines are there in the given figure? Name them. the 5 cm mark of the ruler.
So, the length of the given line segment PQ is 5 cm.
A
H B drawing a line segment
G C
O To draw a line segment of a given length, say 3 cm, we follow these steps.
F
E D Step 1: Place the ruler on a plane paper and hold it with one hand.

0 cm 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Teacher’s Discuss the difference between a line, a line segment and a ray using real-life examples. 0 1 2 3 4 5 6
Tip

122 Mathematics-3